The present invention relates generally to brake-transmission interlock devices for automatic transmission vehicles.
In vehicles operated by an automatic transmission, a gear shift lever is used to alter the position of the transmission gears in order to alter the operating position of the vehicle. Normally, in standard automatic transmissions, the gear shift lever enables the operator to shift the vehicle between the following positions: park, reverse, neutral, drive, second or first.
In order to enhance the safety of automatic transmission vehicles, the industry has advanced several brake-transmission interlock devices, normally actuated by a solenoid. These brake-transmission interlock devices are attached to a shifter base while the solenoid is attached to a separate lever arm.
The purpose of the brake-transmission interlock device is to prevent an operator from shifting the gear shift lever from the park position unless the operator is simultaneously depressing the brake pedal which controls the vehicle's power brakes. Preventing the operator from shifting the vehicle from the park position unless the brake foot pedal is applied prevents the vehicle from inadvertently accelerating in either a forward direction or a reverse direction depending upon the chosen gear. Thus, as the vehicle is moved out of the park position, the transmission-brake interlock device assures that the vehicle is maintained in a stationary position. This stationary position prevents accidents with other vehicles, and/or injury to individuals within the vicinity of the vehicle.
In normal operation, the solenoid is in electrical communication with a control mechanism operably connected to the brake system. When the vehicle is in the park position, the shift lever is maintained in a particular position or notch within the shifter base. When the brake foot pedal is not depressed, the solenoid is in a first position whereby the solenoid drive member maintains the lever arm in a blocking position, and prohibits the shifter from being moved out of the park position. Upon depression of the brake foot pedal, the solenoid is actuated to move the drive member into a second or release position which in turn orients the lever arm so as to enable the shifter to be moved from the park position.
One problem associated with the use of existing brake-transmission interlock devices is the noise associated when the solenoid drive member moves the lever arm to and from the release position. Given the manufacturing tolerances between the solenoid, the lever arm and the shifter base, when the lever arm is moved into the release position, a clicking sound is normally encountered. This clicking sound detracts from the smooth movement of the shifter from the park position and reduces from the perceived quality of the vehicle.
Furthermore, given the separate lever arm and solenoid, over time, manufacturing tolerances have a tendency to reduce the precision with which the brake-transmission interlock device operates. Often, this lack of precision requires replacement or repair, thereby adding cost to the operation of the vehicle. In addition, the use of a separate lever arm increases manufacturing costs.
The solenoid is normally attached to the shifter base by means of pair of thread screws or like fasteners bolted to the shifter base. These fasteners also increase the cost of the brake-transmission interlock device and may loosen during operation, thereby decreasing the precision with which the brake-transmission interlock device functions.
Accordingly, there exists a need for a brake-transmission interlock device having an integrated lever, which is easy to manufacture, install and provides precision movement throughout the life of the vehicle.